The Environment Minister stopped short of branding the head of Government a liar and said his party would continue in coalition until March 11 to ensure the Finance Bill was passed.
Mr Gormley said he warned Mr Cowen in advance that his party would find it hard to support the appointment of five new ministers because it sent out all the wrong signals and would be the “final insult” for the Irish people.
He claimed Mr Cowen had not kept him informed of the decision to press ahead with accepting the resignation of four retiring ministers or the plan to replace them.
“I am always very reluctant to accuse anyone of lying — that would be very unparliamentary. What I am saying is that the version of events that we are giving you is the version that we believe is the correct version.
“I think there is a lot of spinning going on, you always get that. We are not spinning here, which is telling you the plain unvarnished truth. Honestly, I am just telling you what happened,” he said.
Mr Gormley and his colleagues stood up to the Taoiseach yesterday morning when it became clear he would promote backbenchers to the cabinet.
The Green Party said it issued Mr Cowen with an ultimatum that if he insisted on promoting five short-term ministers it would bring down the Government.
Party chairman Dan Boyle said its members felt responsibilities could be shared among ministers and bringing in new faces would suggest jobs being given out for “political advantage”.
This prompted a series of high-stakes meetings between the Green Party delegation (Mr Gormley, his deputy Mary White and Communications Minister Eamon Ryan) and the Taoiseach, Finance Minister Brian Lenihan and Defence Minister Tony Killeen.
After midday the junior coalition partner informed the Taoiseach if he went ahead with his plans to promote five people the proposal would be voted down.
The Greens leadership denied it had given the nod to the proposal 24 hours earlier and insisted when a smaller reshuffle was talked about on Wednesday it objected.
Mr Gormley said Mr Ryan gave the most forceful speech of his life in the meeting with Mr Cowen, Mr Killeen and Government Chief Whip John Curran.
He said the party could “not have been clearer” in its opposition.
“What exact words can you use to convey your dissatisfaction about what is going on?” he said.
Mr Gormley said he left Wednesday’s meeting on the understanding that if appointments were to be made it would be discussed at cabinet first.